Question

Find the circumference of the circle whose area is 25 times the area of the circle with radius 7 cm. 

Answer 1

Area of the circle with radius 7 cm = π r² 

`= 22/7 xx 7 xx 7`

= 154 cm²

Area of new circle = 25 x area of the drde with radius 7 cm 

= 25 x 154 cm² 

= 3850 cm²

Therefore ,

π R² = 3850

R² = `3850 xx 7/22`

R²  = 1225

R = 35 cm

Radius of new circle = 35 cm 

Circumference of new circle = 2 π R

`= 2 xx 22/7 xx 35`

= 220 cm

Hence, Circumference of new circle = 220 cm